Textbook Question
Under certain conditions, the bromination of cyclohexene follows an unusual rate law:
c. What is the overall kinetic order?
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Ch.4 - The Study of Chemical Reactions
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 4, Problem 13a
When a small piece of platinum is added to a mixture of ethene and hydrogen, the following reaction occurs: Ethene
Doubling the concentration of hydrogen has no effect on the reaction rate. Doubling the concentration of ethene also has no effect.
a. What is the kinetic order of this reaction with respect to ethene? With respect to hydrogen? What is the overall order?
Verified step by step guidance1
Step 1: Analyze the reaction provided. The reaction involves ethene (C₂H₄) reacting with hydrogen (H₂) in the presence of a platinum catalyst to form ethane (C₂H₆). This is a catalytic hydrogenation reaction where the double bond in ethene is converted into a single bond in ethane.
Step 2: Understand the experimental observation. Doubling the concentration of ethene or hydrogen has no effect on the reaction rate. This indicates that the reaction rate is independent of the concentrations of these reactants.
Step 3: Recall the concept of reaction order. The kinetic order of a reaction with respect to a reactant is determined by how the rate of reaction changes with the concentration of that reactant. If the rate does not change when the concentration of a reactant is altered, the reaction is zero-order with respect to that reactant.
Step 4: Determine the kinetic order for each reactant. Since the rate is unaffected by changes in the concentration of ethene, the reaction is zero-order with respect to ethene. Similarly, since the rate is unaffected by changes in the concentration of hydrogen, the reaction is zero-order with respect to hydrogen.
Step 5: Calculate the overall order of the reaction. The overall order of a reaction is the sum of the orders with respect to each reactant. Since the reaction is zero-order with respect to both ethene and hydrogen, the overall order of the reaction is 0.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Kinetics and Reaction Order
Kinetics is the study of the rates of chemical reactions and the factors that affect them. The reaction order refers to the power to which the concentration of a reactant is raised in the rate law. It indicates how the rate of reaction is affected by the concentration of reactants. In this case, since doubling the concentrations of both ethene and hydrogen does not change the reaction rate, the reaction is zero-order with respect to both reactants.
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Catalysis
Catalysis involves the acceleration of a chemical reaction by a substance called a catalyst, which is not consumed in the reaction. In this scenario, platinum acts as a catalyst for the hydrogenation of ethene to ethane. The presence of the catalyst lowers the activation energy required for the reaction, allowing it to proceed more quickly without affecting the overall stoichiometry or the reaction order.
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Zero-Order Reactions
A zero-order reaction is one where the rate of reaction is constant and independent of the concentration of the reactants. This means that changes in the concentration of the reactants do not affect the rate of the reaction. In the context of the question, since increasing the concentrations of ethene and hydrogen does not alter the reaction rate, it indicates that the reaction is zero-order with respect to both reactants, leading to an overall zero-order reaction.
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Related Practice
Textbook Question
When a small piece of platinum is added to a mixture of ethene and hydrogen, the following reaction occurs:
Doubling the concentration of hydrogen has no effect on the reaction rate. Doubling the concentration of ethene also has no effect.
b. Write the unusual rate equation for this reaction.
c. Explain this strange rate equation, and suggest what one might do to accelerate the reaction.
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Textbook Question
•CH3 + HCl → CH4 + Cl•
b. What is the activation energy for this reverse reaction?
c. What is the heat of reaction (ΔH°) for this reverse reaction?
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Textbook Question
Draw the reaction-energy diagram for the following reverse reaction:
•CH3 + HCl → CH4 + Cl•
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Textbook Question
Under certain conditions, the bromination of cyclohexene follows an unusual rate law:
b. What is the kinetic order with respect to bromine?
4
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Textbook Question
Under certain conditions, the bromination of cyclohexene follows an unusual rate law:
a. What is the kinetic order with respect to cyclohexene?
2
views